BATTERY PACK

According to the present disclosure, provided is a battery pack that can prevent the surface pressure applied to a cell group at the time of restraint from being uneven, and can stably demonstrate a high level of battery performance. The battery pack disclosed herein includes a cell group in which a plurality of single cells is arranged, and a restraining member that restrains the cell group. Each of the single cells of this battery pack is an all-solid-state cell including a stacked electrode body in which sheet materials composed of a positive electrode, a negative electrode, and a solid electrolyte layer are stacked, and an outer package body that accommodates the stacked electrode body. The cell group of the battery pack disclosed herein is configured such that the ratio of the maximum value K1 of spring constant to the minimum value K2 of spring constant along the arrangement direction (K1/K2) is 1 or more and 3 or less. As a result, the surface pressure applied to the cell group at the time of restraint can be prevented from being uneven, and a high level of battery performance can be exhibited.